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  • #1

    No Acceleration

    I recently rebuilt the carbs with K&L jets from Georgefix using the stock settings of 137.5 mains and 42.5 pilots. I could not get it to idle for the life of me and trying to sync the carbs and get the highest vacuum resulted in no change when screwing or unscrewing the idle mixture screws. Pulled the plugs and 2&3 were darker than 1&4 which were light tan/white. #3 was almost black and there was black residue in the carb throat and throttle plate. Turns out the floats were set low as I had to reset them all.

    #4


    #3


    #2


    #1



    So after reading the jetting recommendations I did the El Cheapo Filter Mod and rejetted with 145 mains and 45 pilots. I reset the floats to exactly 25.7 mm on both sides of the floats and the needles are set to the middle position. The bike idles wonderfully at 1100 and runs pretty well under less than 1/2 throttle up to about 7000 rpm (guess since no tach when riding) and then it will start popping and will not go any further. Also in any gear at any RPM when I roll on the throttle more than half way it will bog down and barely accelerate at all.

    Reading here: http://www.factorypro.com/tech/carbt...m_engines.html

    It sounds like the jet may be too big, but since it doesn't really pull at all, I am hesitant to buy new jets if that is not the real issue.

    Any help?
    79 SF 3H3 Engine, 145/45 Mikuni Jets, El Cheapo Pod Filter Mod w/ EMGO Pods, Coil Repower w/ Dyna Coils, Accell Wires and Side Gapped Plugs, 78 Mech Advance, 4-2 Turnouts
    Tags: None
  • #2
    Originally posted by spayne83 View Post
    I recently rebuilt the carbs with K&L jets from Georgefix using the stock settings of 137.5 mains and 42.5 pilots. I could not get it to idle for the life of me and trying to sync the carbs and get the highest vacuum resulted in no change when screwing or unscrewing the idle mixture screws. Pulled the plugs and 2&3 were darker than 1&4 which were light tan/white. #3 was almost black and there was black residue in the carb throat and throttle plate. Turns out the floats were set low as I had to reset them all.

    #4


    #3


    #2


    #1



    So after reading the jetting recommendations I did the El Cheapo Filter Mod and rejetted with 145 mains and 45 pilots. I reset the floats to exactly 25.7 mm on both sides of the floats and the needles are set to the middle position. The bike idles wonderfully at 1100 and runs pretty well under less than 1/2 throttle up to about 7000 rpm (guess since no tach when riding) and then it will start popping and will not go any further. Also in any gear at any RPM when I roll on the throttle more than half way it will bog down and barely accelerate at all.

    Reading here: http://www.factorypro.com/tech/carbt...m_engines.html

    It sounds like the jet may be too big, but since it doesn't really pull at all, I am hesitant to buy new jets if that is not the real issue.

    Any help?
    Unfortunately the issue is the jets. K&L jets actual hole sizes are larger than equivelant Mikunis. Several have had tuning issues with aftermarket jets (K&L, RD) including myself. Its well documented here with a bit of research. Genuine Mikunis for ALL the jetting on the carb, or it never tune correctly. If your near a Yammy dealer(Mikuni is Yamaha/Kiehn is Honda), order the correct Mikunis(mains, pilots,air jet). The air jet on back of bell is just a SmallMikuni. The K&L jets, having a larger hole size corresponds to your running issues.......too rich everywhere.
    81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

    Comment

    • #3
      Originally posted by spayne83 View Post
      I recently rebuilt the carbs with K&L jets from Georgefix using the stock settings of 137.5 mains and 42.5 pilots. I could not get it to idle for the life of me and trying to sync the carbs and get the highest vacuum resulted in no change when screwing or unscrewing the idle mixture screws. Pulled the plugs and 2&3 were darker than 1&4 which were light tan/white. #3 was almost black and there was black residue in the carb throat and throttle plate. Turns out the floats were set low as I had to reset them all.

      #4


      #3


      #2


      #1



      So after reading the jetting recommendations I did the El Cheapo Filter Mod and rejetted with 145 mains and 45 pilots. I reset the floats to exactly 25.7 mm on both sides of the floats and the needles are set to the middle position. The bike idles wonderfully at 1100 and runs pretty well under less than 1/2 throttle up to about 7000 rpm (guess since no tach when riding) and then it will start popping and will not go any further. Also in any gear at any RPM when I roll on the throttle more than half way it will bog down and barely accelerate at all.

      Reading here: http://www.factorypro.com/tech/carbt...m_engines.html

      It sounds like the jet may be too big, but since it doesn't really pull at all, I am hesitant to buy new jets if that is not the real issue.

      Any help?
      Unfortunately the issue is the jets. K&L jets actual hole sizes are larger than equivelant Mikunis. Several have had tuning issues with aftermarket jets (K&L, RD) including myself. Its well documented here with a bit of research. Genuine Mikunis for ALL the jetting on the carb, or it never tune correctly. If your near a Yammy dealer(Mikuni is Yamaha/Kiehn is Honda), order the correct Mikunis(mains, pilots,air jet). The air jet on back of bell is just a SmallMikuni. The K&L jets, having a larger hole size corresponds to your running issues.......too rich everywhere. Whats wrong with the original jets? Look for the curly little Mikuni logo on them and size. Jets don't wear out. Just clean them in some Pinesol and reuse, if there the size you want.
      81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

      Comment

      • #4
        Wait a minute, if I read this correctly you answered your own issue. You changed from 137.5 main jets and 42.5 pilots up to 145 mains with 45 pilot jets. Your mixture is very rich. You also changed the float heights if I read this correctly, they were low, or closer to the gasket surface.

        So before we go jumping off on the K&L jets being the issue, lets look at the plugs after a run with it popping and carrying on. Try the stock 137.5 main jets with the 42.5 pilots along with the correct float heights. See how that turns out for you.
        Life is what happens while your planning everything else!

        When your work speaks for itself, don't interrupt.

        81 XS1100 Special - Humpty Dumpty
        80 XS1100 Special - Project Resurrection


        Previously owned
        93 GSX600F
        80 XS1100 Special - Ruby
        81 XS1100 Special
        81 CB750 C
        80 CB750 C
        78 XS750

        Comment

        • #5
          Just pulled the plugs and they are (sitting on the bike, left to right)

          #1



          #2



          #3



          #4



          So 1&2 are looking ok with the 145/45 jetting, but 3&4 are still looking rich. There are less than 25 miles on these plugs with the 145/45 jetting, but #3 stills looks just as rich as before.

          I'm guessing that the TCI being wrong would be a major contributing factor, so I will start with the stock jets and go from there when I get the new TCI in.
          79 SF 3H3 Engine, 145/45 Mikuni Jets, El Cheapo Pod Filter Mod w/ EMGO Pods, Coil Repower w/ Dyna Coils, Accell Wires and Side Gapped Plugs, 78 Mech Advance, 4-2 Turnouts

          Comment

          • #6
            What air filter system and exhaust system are you running spayne?

            I have aftermarket exhaust and the stock air box on both of my running XSs and I went up 1 size (140 mains and 45 pilots) and they both run great.

            You most definitely need to go with genuine Mikuni jets though. Aftermarket jets never seem to work correctly.
            Greg

            Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

            ― Albert Einstein

            80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

            The list changes.

            Comment

            • #7
              Aftermarket 4 into 2 turnouts with EMGO pod filters fitted on the stock boots so there is no issue with air flow through the filters.

              Once the TCI comes in I will try to tune with the current K&L jets and if that doesn't work I'll order some larger mains (140 or 142.5) and use the 45 pilots, as it was idling just fine with the 45s.
              79 SF 3H3 Engine, 145/45 Mikuni Jets, El Cheapo Pod Filter Mod w/ EMGO Pods, Coil Repower w/ Dyna Coils, Accell Wires and Side Gapped Plugs, 78 Mech Advance, 4-2 Turnouts

              Comment

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